Drink supply systems for supplying a dispensing machine with cold drink, such as cold water supplied from city water, or cold carbonated drinks to dilute syrup in a cup, must generally be maintained hygienically, so as to prevent propagation of bacteria and the like. There has been known a drink water sterilization means for this purpose, as disclosed in Japanese Patent Early Publication No. 61-283391.
Said sterilization means comprises a pair of electrodes, through which city water is passed to a cistern. Said electrodes are impressed with a DC voltage for electrolysis of the water stored in the cistern, the water being supplied to a drink supply system after it is cooled.
This prior art is based on the fact that, since city water contains chlorine ions (Cl.sup.-), aforementioned electrolysis will generate chlorine molecules (Cl.sub.2) according to the following chemical reaction: EQU 2Cl.sup.- .fwdarw.Cl.sub.2 +2e.
The chlorine molecules (Cl.sub.2) thus generated is easily dissolved in the drink (H.sub.2 O) to form hypochlorous acid (HClO) by the reaction: EQU Cl.sub.2 +H.sub.2 O.fwdarw.HClO+HCl.
Since the hypochlorous acid (HClO) formed has sterilization effect, it may sterilize the water in the cistern and the drink supply line.
Such drink supply systems, however, have dispensing nozzles and drink supply valves open to the air, which tend to be unsanitary due to contamination with bacteria. Despite of the fact, the pair of the electrodes for generating hypochlorous acid (HClO) are arranged in the proximity of the cistern in the above drink supply system.
As a result, the hypochlorous acid (HClO) generated in the cistern is passed through a long line to lose its sterilization effect when reached near the dispensing nozzles, and cannot effectively sterilize bacteria propagating at the drink supply valves.